1. Field of the Invention
The present invention relates to a dual clutch transmission apparatus that controls a plurality of clutches, and to a motorcycle and a start control method.
2. Description of the Related Art
Conventional multi-stage vehicle transmissions having a plurality of clutches enabling fast gear change on automobiles are known (see, for example, Japanese Patent Application Laid-Open No. 58-124851).
In a multi-stage vehicle transmission disclosed in Japanese Patent Application Laid-Open No. 58-124851, a first clutch connects and disconnects an input shaft that receives the driving force of an engine to and from a first main shaft provided rotatably on the input shaft, and a second clutch connects and disconnects an input shaft to and from a second main shaft provided coaxially with the input shaft.
In this multi-stage vehicle transmission, a sub shaft connected to an output shaft is disposed parallel to the input shaft, the first main shaft and the second main shaft. This enables transmission at a predetermined gear ratio from either the first main shaft or the second main shaft to the sub shaft through a plurality of gears by the connection of either the first clutch or the second clutch. The output shaft connected to the sub shaft is thereby rotated to output a driving force.
Thus, in the above-described multi-stage vehicle transmission, the rotation speed of the output shaft is changed by selectively connecting the first clutch and the second clutch to transmit a torque on the input shaft to the sub shaft at a different gear ratio, without blocking power at the time of gear change.
In recent years, there has been a demand for providing a motorcycle having a limited mount space, with a multi-stage vehicle transmission having a plurality of clutches mounted on an automobile. To mount such a multi-stage vehicle transmission having a plurality of clutches on a motorcycle, it is desirable that the transmission itself is downsized.
In a transmission, a clutch is connected and disconnected on the basis of the state of engagement between a drive-side member and a first main shaft-side member (the relative position of the two members) and has a comparatively large weight as a member of a drive transmission system.
In an arrangement having a plurality of such clutches, the weight of the multi-stage transmission itself may be increased in comparison with a multi-stage transmission having one clutch. This leads to a need for providing a transmission that has a small size by reducing the size of a clutch itself.
The size of a clutch is proportional to a thermal load at which the clutch can withstand frictional heat generated in a half-engaging state (in which the clutch slips while transmitting a torque) in connection with and disconnection of the clutch, particularly frictional heat generated at the start of the drive operation upon changing from a neutral (N) position to a first gear position. That is, to have a thermal load at which it can withstand frictional heat generated in a half-engaging state, it is required to increase the sizes of each of the drive-side member and the driven-side member, which are to be half-engaged.
That is, in such an arrangement in which clutches are simply reduced in size, a multi-stage transmission cannot withstand a thermal load at the start of the drive operation. Thus, the multi-stage transmission requires larger clutches having a size so as to be capable of operating under the thermal load at the start of the drive operation, which causes the transmission to become heavier.